This study is one of the first COVID-19 related bus studies to fully characterize cough aerosol dispersion and control in the highly turbulent real-world environment of driving regular bus routes on both a school bus and a transit bus. While several other bus studies have been conducted, they were limited to clinical contact tracing, simulation, or partial characterization of aerosol transmission in the passenger areas with constraint conditions. When considering the risk of transmission of SARS-CoV-2 (COVID-19) and other highly infectious airborne diseases, ground based public transportation systems are high-risk environments for airborne transmission particularly since social distancing of six feet is not practical on most buses. This study demonstrates that wearing of masks reduced the overall particle count released into the bus by an average of 50% or more depending on mask quality and reduced the dispersion distance by several feet. The study also demonstrates an 84.36% reduction in aerosol particles and an 80.28% reduction in the mean aerosol residence time for some test cases. We conducted 84 experimental runs using nebulized 10% sodium chloride and a mechanical exhalation simulator that resulted in 78.3 million data points and 124 miles of on-the-road testing. Our study not only captures the dispersion patterns using 28 networked particle counters, as well as quantifies the effectiveness of using on-board fans, opening of various windows, use of face coverings or masks, and the use of the transit bus HVAC system. This work also provides empirical observations of aerosol dispersion in a real-world turbulent air environment, which are remarkably different than many existing fluid dynamics simulations, and also offers substantial discussion on the implications for inclement weather conditions, driver safety, retrofit applications to improve bus air quality, and operational considerations for public transportation organizations.

The COVID-19 (SARS-CoV-2) pandemic is overwhelming global healthcare delivery systems due to the exponential spike in cases requiring specialty tests, facilities and equipment, including complex, precision devices like ventilators. In particular, the surge in critically ill patients has revealed a significant deficiency in regional availability of respiratory care ventilators. The authors offer a mathematical framework for ventilator distribution under scarcity conditions using an optimized network model and solver. The framework is interoperable with existing COVID-19 healthcare demand models and scales for different user-defined system sizes, including hospital networks, city, state, regional and national-scale prioritization. The authors' approach improves current capabilities for medical device resource management within the existing incident command system while accounting for availability of devices, ventilation treatment time periods, disinfection and cleaning between patients, as well as shipping logistics time. The authors present a proof of concept using a high fidelity COVID-19 data set from Colorado, discusses how to scale nationally, and emphasizes the importance of applying ethical human-in-the-loop decision making when using this or similar approaches to managing medical device resources during epidemic emergencies.

Objective: To determine the effectiveness of non-medical grade washable masks or face coverings in controlling airborne dispersion from exhalation (both droplet and aerosol), and to aid in establishing public health strategies on the wearing of masks to reduce COVID-19 transmission. Design: This comparative effectiveness study using an exhalation simulator to conduct 94 experiment runs with combinations of 8 different fabrics, 5 mask designs, and airflows for both talking and coughing. Setting: Non-airtight fume hood and multiple laser scattering particle sensors. Participants: No human participants. Exposure: 10% NaCl nebulized solution delivered by an exhalation simulator through various masks and fabrics with exhalation airflows representative of "coughing" and "talking or singing." Main Outcomes and Measures: The primary outcome was reduction in aerosol dispersion velocity, quantity of particles, and change in dispersion direction. Measurements used in this study included peak expiratory flow (PEF), aerosol velocity, concentration area under curve (AUC), and two novel metrics of expiratory flow dispersion factor (EDF) and filtration efficiency indicator (FEI). Results: Three-way multivariate analysis of variance establishes that factors of fabric, mask design, and exhalation breath level have a statistically significant effect on changing direction, reducing velocity or concentration (Fabric: P = < .001, Wilks' Λ = .000; Mask design: P = < .001, Wilks' Λ = .000; Breath level: P = < .001, Wilks' Λ = .004). There were also statistically significant interaction effects between combinations of all primary factors. Conclusions and Relevance: The application of facial coverings or masks can significantly reduce the airborne dispersion of aerosolized particles from exhalation. The results show that wearing of non-medical grade washable masks or face coverings can help increase the effectiveness of non-pharmaceutical interventions (NPI) especially where infectious contaminants may exist in shared air spaces. However, the effectiveness varies greatly between the specific fabrics and mask designs used.